Refrigerators such as Stirling refrigerators and pulse pipe refrigerators require a pressure fluctuation source for creating pressure fluctuation in a refrigerating fluid inside the refrigerator. In recent years, linear compressors have been receiving attention as an instrument for providing such pressure fluctuations. A linear compressor of this kind is disclosed in Japanese Patent Publication No. H,7-88986, which will now be described on the basis of FIG. 4.
FIG. 4 shows an example of a linear compressor applied to a Stirling refrigerator. In the figure, a Stirling refrigerator 70 is basically made up of a compressor 71, a cold finger 72 and a connecting pipe 73 connecting these together. Of these, the compressor 71 has a first cylinder 73a and a first piston 74a and a second cylinder 73b and a second piston 74b, contained inside a housing 71a. A partition wall 75 is disposes between the first cylinder 73a and the second cylinder 73b. The first piston 74a and the second piston 74b are positioned by support springs 76a, 76b, respectively, and reciprocate, respectively, inside the first cylinder 73a and the second cylinder 73b.
Lightweight first and second sleeves 77a and 77b made of a non-magnetic material are connected to the first piston 74a and the second piston 74b, respectively, and conductors are wound around these sleeves to form a first moving coil 78a and a second moving coil 78b. Permanent magnets 79a, 79b and yokes 80a, 80b are also provided inside the housing 71a and together these constitute a magnetic circuit.
In this construction, when a sine wave current is passed through the first moving coil 78a and the second moving coil 78b so that they vibrate with the same amplitude in mutually opposite directions, the two pistons 74a, 74b reciprocate inside the cylinders 73a, 73b in opposite directions and impart a sine wave motion to a gas pressure inside the working space between them. Flow changes of gas passing through a displacer 82 and a regenerator 83 accompanying this sine wave gas wave motion cause the displacer 82 containing the regenerator 83 to reciprocate axially inside the cold finger 72 at the same frequency as the pistons 74a, 74b but with a different phase.
When the pistons 74a, 74b and the displacer 82 move while maintaining a suitable phase difference, the working gas sealed inside the working space goes through a known thermodynamic cycle called the reverse Stirling cycle, and removes heat mainly from a low-temperature chamber 81 of the cold finger 72.
In the linear compressor of the related device described above, opposing pistons are used; however, with this kind of construction, because the compression space, which reaches high temperatures and high pressures, formed between the pistons is positioned in the approximate center of the compressor, it is difficult for heat produced in the compression space to be radiated to the outside. Consequently, there has been the problem that the temperature of the working gas is raised by heat produced in the compression space and the refrigerating capacity of the refrigerator deteriorates.